"I would say in the next decade, it wouldn't surprise me if [the 100-meter record] goes below 9 seconds," professor Peter Weyand, a physiologist at Southern Methodist University in Dallas, tells NPR's Melissa Block. "It could go faster than that — and it probably will."

Weyand, who specializes in the biomechanics of running, says the body's speed depends on how fast the muscles are able to "turn on."

"And we know biologically we're not anywhere close to that limit," Weyand says.